EP0870848A1 - Niobium containing steel and process for making flat products from this steel - Google Patents

Niobium containing steel and process for making flat products from this steel Download PDF

Info

Publication number
EP0870848A1
EP0870848A1 EP98200844A EP98200844A EP0870848A1 EP 0870848 A1 EP0870848 A1 EP 0870848A1 EP 98200844 A EP98200844 A EP 98200844A EP 98200844 A EP98200844 A EP 98200844A EP 0870848 A1 EP0870848 A1 EP 0870848A1
Authority
EP
European Patent Office
Prior art keywords
niobium
steel
maximum
content
temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP98200844A
Other languages
German (de)
French (fr)
Other versions
EP0870848B1 (en
Inventor
Philippe Harlet
Helmut Ruhl
Firmin Beco
Heiko Reichelt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ArcelorMittal Liege Upstream SA
Original Assignee
Cockerill Sambre SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Family has litigation
First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=3890428&utm_source=***_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=EP0870848(A1) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Application filed by Cockerill Sambre SA filed Critical Cockerill Sambre SA
Publication of EP0870848A1 publication Critical patent/EP0870848A1/en
Application granted granted Critical
Publication of EP0870848B1 publication Critical patent/EP0870848B1/en
Anticipated expiration legal-status Critical
Revoked legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
    • C21D8/0426—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/041—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing involving a particular fabrication or treatment of ingot or slab
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
    • C21D8/0436—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
    • C21D8/0473—Final recrystallisation annealing

Definitions

  • Titanium-free steel indicated in EP-A-0421087, is a steel with ultra-low carbon content, i.e. less than 0.007% by weight, wherein the Nb content is very much higher than the content in nitrogen, of the order of 20 times. Nitrogen is therefore in this steel entirely fixed by nitrobutene niobium and, if boron is used, it remains free and not nitrided. Boron is intended to protect the joints from ferritic grains in order to avoid brittleness to the cold deformation. This steel allows the development to obtain a sheet equivalent or close to IF steels (interstitial free) which have coefficients very high drawing depth, but also a very ⁇ r high (strong plane anisotropy).
  • EP-0101740 it is proposed to manufacture flat products whose Nb content is less than or equivalent to the N content. Following hot rolling at a final temperature below Ar 3 , rolling when cold and annealed, products are obtained having low mechanical strength properties, sometimes even lower than the usual minimum requirements.
  • a niobium steel is manufactured, in which the Nb content must be at least 6 times that of nitrogen.
  • the manufacturing process here also includes hot rolling at a final temperature below Ar 3 , cold rolling and annealing, as well as baking after application of varnish.
  • the final products obtained have a much higher niobium content, for properties of mechanical resistance that are not much improved.
  • EP-B-0400031 finally proposes, by way of comparative example, a titanium-free niobium steel, having a content comprising more than 12 times the N content. Following hot rolling at a temperature final higher than Ar 3 , cold rolling and annealing, a product is obtained which, according to the patent itself, is not suitable for deep drawing, whatever the degrees of reduction used during cold rolling.
  • the object of the present invention is to provide a niobium steel having, in terms of properties mechanical on cold-rolled and annealed strips, a favorable compromise between the properties of resistance, such as for example the elastic limit and the breaking load, and the properties of ductility, such as uniform elongation, coefficient total hardening and elongation.
  • niobium steel as described at the beginning, characterized in that this steel contains a stoichiometric niobium content less than that of nitrogen and a boron or zirconium content sufficient to fix nitrogen not fixed by niobium.
  • This steel has the advantage of being able have a low niobium content, and therefore not to alter the ductility properties of steel, while obtaining a secure fixation and preferably early nitrogen by the simultaneous presence of boron or zirconium and niobium.
  • the content in niobium is at most equal to four times the N content, preferably three times the latter.
  • the steel contains an Nb content of less than 0.040% by weight, and preferably between 0.005 and 0.030% by weight.
  • it contains a boron content between 0.0005 and 0.012% by weight, preferably between 0.0015 and 0.012% by weight, or a zirconium content between 0.020 and 0.080% by weight.
  • the carbon content is equal to or greater than 0.010% by weight.
  • the amount of Nb can well be relatively small compared to the content carbon which allows obtaining a steel with favorable mechanical properties.
  • This process offers the advantage of fixing supplied with nitrogen in the form of boron nitride or of zirconium as well as in the form of carbonitride niobium, and this at a very early stage in the process.
  • the simultaneous presence of boron or zirconium and niobium also promotes reduced grain size austenitic during hot rolling.
  • the niobium present is advantageously redissolved.
  • the final temperature of hot rolling is preferably equal to or less than 900 ° C. It is precisely at this temperature, that is to say between the transformation temperature ⁇ ⁇ ⁇ (AR 3 ) and 900 ° C, that the boron nitrides and the carbon nitrides of Nb precipitate in the process according to the invention, which fixes the nitrogen.
  • the maximum temperature mentioned above is not, however, critical and should only be considered as a preferred temperature.
  • the reduction rate is of the order of 40 to 85%, preferably 55-80%.
  • the niobium steel according to the invention is usually a steel produced by conversion or of electrical production, classic, which is cast in continued.
  • This steel must be extra soft, i.e. have an extremely low carbon content, less than 0.100% by weight, reaching up to minimum contents up to 0.020% or more.
  • the carbon content will not exceed not less than 0.010% by weight.
  • This steel must also be calmed with aluminum with a content of less than 0.080% by weight.
  • Nb, B and Zr are calculated mainly as a function of nitrogen present in the steel being processed.
  • Nb added is therefore in reality significantly lower stoichiometrically than nitrogen.
  • Nitrogen not fixed by niobium is fixed by B or Zr, which allows an addition of Nb lower than what is usually necessary to obtain properties of sufficient mechanical resistance from a niobium steel, titanium free. This minimal addition of Nb makes it possible to maintain good ductility properties. It also offers advantages economical considering the cost not negligible niobium.
  • the steel described above is poured into slabs, which are reheated in a conventional oven, for example a traveling beam oven or a pushing oven, for that they reach a higher temperature at heart or equal to 1000 ° C, which is enough to restore solution of the precipitated niobium.
  • a conventional oven for example a traveling beam oven or a pushing oven
  • the strip is then cooled so controlled and finally wound at a temperature of around from 625 ° C ⁇ 125 ° C.
  • the strip After continuous pickling in conventional lines (HC1 or H 2 SO 4 ), the strip is cold re-rolled, with a thickness reduction rate of between 40 and 85%.
  • the cold rolled strip is then subjected to recrystallization annealing to give it the mechanical properties required.
  • This annealing can take the form of static annealing, for example in a tight or expanded coil, at a temperature of around 620-680 ° C, or in the form of continuous annealing at a temperature of 680-850 ° C.
  • Last annealing can be combined or not with a possible recovery by dip coating or other processes.
  • a final rolling step is still performed, in the form of a final work hardening, in order to remove the phenomena of "Lüders bands" and ensure good surface roughness as well as flatness of the product.
  • Niobium steel with extremely low carbon content without boron.
  • Chemical composition (10 -3 %) VS Mn Yes P S Al N 2 B Nb 50 350 8 12 6 40 6.0 0 50
  • Niobium steel according to the invention with addition of boron.
  • Chemical composition (10 -3 %) VS Mn Yes P S Al N 2 B Nb 55 300 7 14 3 50 5.6 4.5 7
  • Niobium steel according to the invention with addition of boron.
  • Chemical composition (10 -3 %) VS Mn Yes P S Al N 2 B Nb 45 270 19 12 6 43 6.0 4.0 12
  • Niobium steel with extremely low carbon content with the addition of zirconium.
  • Chemical composition (10 -3 %) VS Mn Yes P S Al N 2 B Nb Zr 35 200 5 9 4 47 4.9 0 10 30
  • Niobium steels according to the invention offer both mechanical resistance properties well above the lower limits usual and good ductility properties, in therefore providing an entirely favorable compromise for subsequent treatments.
  • the niobium steels according to the invention have, on cold-rolled and annealed strips, mechanical properties in the band plane which are significantly independent of management compared to in the sense of rolling as well as a rational contraction in width substantially identical to a contraction rational in thickness. They therefore bring together all conditions for undergoing stamping type treatments difficult and others.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Catalysts (AREA)
  • Heat Treatment Of Steel (AREA)
  • Compositions Of Oxide Ceramics (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

Extra mild niobium steel is free of titanium and comprises no more than following by weight: 0.100% carbon, 1.000% manganese, 0.100% phosphorous, 0.020% sulphur, 0.080% aluminium, 0.012% nitrogen and 0.500% silicon, plus an amount of niobium stoichiometrically less than the N content and enough boron or zirconium to fix all the N which is not fixed by the Nb. The rest is iron plus any impurities. Also claimed is casting the steel into a slab at least 1000 degrees C, then hot rolling to form a strip with a final rolling temperature above Ar3, winding into a reel between 500 and 750 degrees C, cold rolling to the desired thickness, annealing to recrystallise and finally shaping the finished article.

Description

La présente invention est relative à un acier au niobium, extra doux, calmé à l'aluminium et exempt de titane, pour produits plats laminés à froid et recuits, présentant une composition chimique en % en poids comprenant :

  • au maximum 0,100 % de C,
  • au maximum 1,000 % de Mn,
  • au maximum 0,100 % de P,
  • au maximum 0,020 % de S,
  • au maximum 0,080 % de Al,
  • au maximum 0,012 % de N,
  • au maximum 0,500 % de Si,
    •    le reste étant du fer et des impuretés résiduelles.The present invention relates to a niobium steel, extra soft, calmed with aluminum and free from titanium, for cold-rolled and annealed flat products, having a chemical composition in% by weight comprising:
  • maximum 0.100% of C,
  • maximum 1,000% of Mn,
  • maximum 0.100% of P,
  • maximum 0.020% of S,
  • maximum 0.080% Al,
  • maximum 0.012% of N,
  • maximum 0.500% of Si,
    • the remainder being iron and residual impurities.

    On connaít déjà depuis longtemps des aciers au niobium de ce genre (voir par exemple EP-0101740, DE-19547181 et EP-A-0421087).Steels have been known for a long time niobium of this kind (see for example EP-0101740, DE-19547181 and EP-A-0421087).

    L'acier exempt de titane, indiqué dans la EP-A-0421087, est un acier à teneur ultrabasse en carbone, à savoir inférieure à 0,007 % en poids, dans lequel la teneur en Nb est très largement supérieure à la teneur en azote, de l'ordre de 20 fois. L'azote est donc dans cet acier entièrement fixé par le niobium nitrurigène et, si du bore est utilisé, il reste libre et non nitruré. Le bore est prévu pour protéger les joints des grains ferritiques en vue d'éviter la fragilite à la déformation à froid. Cet acier permet à l'élaboration d'obtenir une tôle équivalente ou proche des aciers IF (interstitiel free) qui présentent des coéfficients d'emboutissage r très élevés, mais également un Δr très élevé (forte anisotropie plane).Titanium-free steel, indicated in EP-A-0421087, is a steel with ultra-low carbon content, i.e. less than 0.007% by weight, wherein the Nb content is very much higher than the content in nitrogen, of the order of 20 times. Nitrogen is therefore in this steel entirely fixed by nitrobutene niobium and, if boron is used, it remains free and not nitrided. Boron is intended to protect the joints from ferritic grains in order to avoid brittleness to the cold deformation. This steel allows the development to obtain a sheet equivalent or close to IF steels (interstitial free) which have coefficients very high drawing depth, but also a very Δr high (strong plane anisotropy).

    Dans le EP-0101740, on propose de fabriquer des produits plats dont la teneur en Nb est inférieure ou équivalente à la teneur en N. A la suite d'un laminage à chaud à une température finale inférieure à Ar3, d'un laminage à froid et d'un recuit, on obtient des produits présentant des propriétés mécaniques de résistance faibles, parfois même inférieures aux exigences minimales usuelles.In EP-0101740, it is proposed to manufacture flat products whose Nb content is less than or equivalent to the N content. Following hot rolling at a final temperature below Ar 3 , rolling when cold and annealed, products are obtained having low mechanical strength properties, sometimes even lower than the usual minimum requirements.

    Dans le DE-19547181, on fabrique un acier au niobium, dans lequel la teneur en Nb doit être au minimum 6 fois celle de l'azote. Le procédé de fabrication comprend ici aussi un laminage à chaud à une température finale inférieure à Ar3, un laminage à froid et un recuit, ainsi qu'une cuisson après application de vernis. Les produits finals obtenus présentent une teneur nettement supérieure en niobium, pour des propriétés de résistance mécanique peu améliorées.In DE-19547181, a niobium steel is manufactured, in which the Nb content must be at least 6 times that of nitrogen. The manufacturing process here also includes hot rolling at a final temperature below Ar 3 , cold rolling and annealing, as well as baking after application of varnish. The final products obtained have a much higher niobium content, for properties of mechanical resistance that are not much improved.

    Dans le EP-B-0400031 on propose enfin, à titre d'exemple comparatif, un acier au niobium sans titane, présentant une teneur comportant plus de 12 fois la teneur en N. A la suite d'un laminage à chaud à une température finale supérieure à Ar3, d'un laminage à froid et d'un recuit, on obtient un produit qui, de l'avis même de la brevetée, n'est pas approprié pour un emboutissage profond, quel que soit les degrés de réduction utilisés au cours du laminage à froid.EP-B-0400031 finally proposes, by way of comparative example, a titanium-free niobium steel, having a content comprising more than 12 times the N content. Following hot rolling at a temperature final higher than Ar 3 , cold rolling and annealing, a product is obtained which, according to the patent itself, is not suitable for deep drawing, whatever the degrees of reduction used during cold rolling.

    La présente invention a pour but de proposer un acier au niobium présentant, en terme de propriétés mécaniques sur des bandes relaminées à froid et recuites, un compromis favorable entre les propriétés de résistance, telles que par exemple la limite d'élasticité et la charge de rupture, et les propriétés de ductilité, telles que l'allongement uniforme, le coefficient d'écrouissage et l'allongement total.The object of the present invention is to provide a niobium steel having, in terms of properties mechanical on cold-rolled and annealed strips, a favorable compromise between the properties of resistance, such as for example the elastic limit and the breaking load, and the properties of ductility, such as uniform elongation, coefficient total hardening and elongation.

    Pour résoudre ces problèmes, on a prévu suivant l'invention un acier au niobium tel que décrit au début, caractérisé en ce que cet acier contient une teneur en niobium stoechiométriquement inférieure à celle de l'azote et une teneur en bore ou en zirconium suffisante pour fixer l'azote non fixé par le niobium.To solve these problems, we planned according to the invention a niobium steel as described at the beginning, characterized in that this steel contains a stoichiometric niobium content less than that of nitrogen and a boron or zirconium content sufficient to fix nitrogen not fixed by niobium.

    Cet acier présente l'avantage de pouvoir présenter une teneur en niobium peu élevée, et donc de ne pas altérer les propriétés de ductilité de l'acier, tout en obtenant une fixation assurée et de préférence précoce de l'azote par la présence simultanée de bore ou de zirconium et de niobium. Avantageusement, la teneur en niobium est au maximum égale au quadruple de la teneur en N, de préférence au triple de celle-ci.This steel has the advantage of being able have a low niobium content, and therefore not to alter the ductility properties of steel, while obtaining a secure fixation and preferably early nitrogen by the simultaneous presence of boron or zirconium and niobium. Advantageously, the content in niobium is at most equal to four times the N content, preferably three times the latter.

    Suivant une forme de réalisation de l'invention, l'acier contient une teneur en Nb inférieure à 0,040 % en poids, et de préférence comprise entre 0,005 et 0,030 % en poids. Avantageusement, il contient une teneur en bore comprise entre 0,0005 et 0,012 % en poids, de préférence entre 0,0015 et 0,012 % en poids, ou encore une teneur en zirconium comprise entre 0,020 et 0,080 % en poids.According to one embodiment of the invention, the steel contains an Nb content of less than 0.040% by weight, and preferably between 0.005 and 0.030% by weight. Advantageously, it contains a boron content between 0.0005 and 0.012% by weight, preferably between 0.0015 and 0.012% by weight, or a zirconium content between 0.020 and 0.080% by weight.

    Suivant une forme de réalisation particulière de l'invention, la teneur en carbone est égale ou supérieure à 0,010 % en poids. La quantité de Nb peut ainsi être relativement faible par rapport à la teneur en carbone ce qui permet l'obtention d'un acier à propriétés mécaniques favorables.According to a particular embodiment of the invention, the carbon content is equal to or greater than 0.010% by weight. The amount of Nb can well be relatively small compared to the content carbon which allows obtaining a steel with favorable mechanical properties.

    D'autres formes de réalisation particulières de l'acier suivant l'invention ressortiront des revendications 1 à 11 données ci-après.Other specific embodiments of the steel according to the invention will emerge from the claims 1 to 11 data below.

    L'invention concerne également un procédé de fabrication de produits plats laminés à froid et recuits, à base d'un acier au niobium présentant une composition chimique telle qu'indiquée ci-dessus. Ce procédé comprend

  • une coulée de cet acier en brames,
  • un réchauffaqe des brames à une température supérieure ou égale à 1000°C,
  • un laminage à chaud des brames pour former des bandes, avec une température finale de laminage supérieure à Ar3,
  • un bobinage des bandes à une température de bobinage comprise entre 500 et 750°C,
  • un laminage à froid des bandes avec un taux de réduction prédéterminé,
  • un recuit de recristallisation, et
  • un passage d'écrouissage final (de peau).
    • The invention also relates to a method for manufacturing cold-rolled and annealed flat products, based on a niobium steel having a chemical composition as indicated above. This process includes
  • a casting of this steel in slabs,
  • reheating the slabs to a temperature greater than or equal to 1000 ° C.,
  • hot rolling of the slabs to form strips, with a final rolling temperature higher than Ar 3 ,
  • winding the strips at a winding temperature between 500 and 750 ° C,
  • cold rolling of the strips with a predetermined reduction rate,
  • recrystallization annealing, and
  • a final work hardening passage (skin).

    • Ce procédé offre l'avantage d'une fixation assurée de l'azote sous la forme de nitrure de bore ou de zirconium ainsi que sous la forme de carbonitrure de niobium, et cela à un stade très précoce dans le processus. La présence simultanée de bore ou de zirconium et de niobium favorise en outre une taille réduite du grain austénitique pendant le laminage à chaud. A la température de réchauffage utilisée, le niobium présent est avantageusement remis en solution.This process offers the advantage of fixing supplied with nitrogen in the form of boron nitride or of zirconium as well as in the form of carbonitride niobium, and this at a very early stage in the process. The simultaneous presence of boron or zirconium and niobium also promotes reduced grain size austenitic during hot rolling. At the temperature used for reheating, the niobium present is advantageously redissolved.

    Suivant une forme de réalisation de l'invention, la température finale de laminage à chaud est de préférence égale ou inférieure à 900°C. C'est précisement à cette température, c'est-à-dire entre la température de transformation γ → α (AR3) et 900°C, que les nitrures de bore et les carbonitrures de Nb précipitent dans le procédé suivant l'invention, ce qui fixe l'azote. La température maximale citée ci-dessus n'est toutefois pas critique et elle ne doit être considérée que comme une température préférentielle. According to one embodiment of the invention, the final temperature of hot rolling is preferably equal to or less than 900 ° C. It is precisely at this temperature, that is to say between the transformation temperature γ → α (AR 3 ) and 900 ° C, that the boron nitrides and the carbon nitrides of Nb precipitate in the process according to the invention, which fixes the nitrogen. The maximum temperature mentioned above is not, however, critical and should only be considered as a preferred temperature.

    Suivant une forme de réalisation préférée de l'invention, pendant le laminage à froid, le taux de réduction est de l'ordre de 40 à 85 %, de préférence de 55-80 %. Ce taux de réduction est calculé suivant la formule : Taux de réduction = Epaisseur fin laminage chaud - épaisseur fin laminage Epaisseur fin laminage chaud According to a preferred embodiment of the invention, during cold rolling, the reduction rate is of the order of 40 to 85%, preferably 55-80%. This reduction rate is calculated according to the formula: Reduction rate = Thickness at the end of hot rolling - thickness at the end of rolling Thickness of hot rolling end

    D'autres modes de réalisation particuliers de procédé suivant l'invention ressortiront des revendications 12 à 19 données ci-après.Other particular embodiments of process according to the invention will emerge from the claims 12 to 19 given below.

    D'autres détails et particularités de l'invention ressortiront de la description donnée ciaprès à titre non limitatif.Other details and peculiarities of the invention will emerge from the description given below without limitation.

    L'acier au niobium suivant l'invention est usuellement un acier d'élaboration par conversion ou d'élaboration électrique, classique, qui est coulé en continu. Cet acier doit être extra doux, c'est-à-dire présenter une teneur en carbone extrêmement basse, inférieure à 0,100 % en poids, en pouvant atteindre des teneurs minimales jusqu'à 0,020 % ou davantage. Avantageusement toutefois la teneur en carbone ne dépassera pas une valeur inférieure à 0,010 % en poids.The niobium steel according to the invention is usually a steel produced by conversion or of electrical production, classic, which is cast in continued. This steel must be extra soft, i.e. have an extremely low carbon content, less than 0.100% by weight, reaching up to minimum contents up to 0.020% or more. Advantageously however the carbon content will not exceed not less than 0.010% by weight.

    Cet acier doit aussi être calmé à l'aluminium avec une teneur inférieure à 0,080 % en poids.This steel must also be calmed with aluminum with a content of less than 0.080% by weight.

    Il comprendra bien entendu du niobium et sera exempt de toute addition de titane.It will of course include niobium and will free of any addition of titanium.

    La composition chimique de cet acier pourra donc être la suivante, en % en poids :

  • 0,010 < C < 0,100
  • 0,100 < Mn < 1,000
  • P < 0,100
  • S < 0,020
  • Al < 0,080
  • N < 0,012
  • Si < 0,500
    • avec des additions volontaires de niobium combinées à une addition de bore ou de zirconium, de par exemple :
  • Nb ≤ 0,040 % en poids, et de
  • 0,0015 ≤ B ≤ 0,0120 % en poids
       ou de
  • 0,020 ≤ Zr ≤ 0,080 % en poids,
    •  le reste étant du fer et des impuretés résiduelles de Cu, Ni, Cr, Sn par exemple.The chemical composition of this steel could therefore be as follows, in% by weight:
  • 0.010 <C <0.100
  • 0.100 <Mn <1.000
  • P <0.100
  • S <0.020
  • Al <0.080
  • N <0.012
  • If <0.500
    • with voluntary additions of niobium combined with an addition of boron or zirconium, for example:
  • Nb ≤ 0.040% by weight, and
  • 0.0015 ≤ B ≤ 0.0120% by weight
    or from
  • 0.020 ≤ Zr ≤ 0.080% by weight,
    • the remainder being iron and residual impurities of Cu, Ni, Cr, Sn for example.

    En fait les valeurs ajustées de Nb, de B et de Zr se calculent principalement en fonction de l'azote présent dans l'acier en cours de traitement.In fact the adjusted values of Nb, B and Zr are calculated mainly as a function of nitrogen present in the steel being processed.

    La quantité de Nb ajoutée est donc en réalité nettement inférieure stoechiométriquement à l'azote. L'azote non fixé par le niobium l'est par le B ou le Zr, ce qui permet une addition de Nb inférieure à ce qui est habituellement nécessaire, pour obtenir des propriétés de résistance mécaniques suffisantes de la part d'un acier au niobium, sans titane. Cette addition minimale de Nb permet de maintenir simultanément de bonnes propriétés de ductilité. Elle offre en outre des avantages économiques appréciables étant donné le coût non négligeable du niobium.The amount of Nb added is therefore in reality significantly lower stoichiometrically than nitrogen. Nitrogen not fixed by niobium is fixed by B or Zr, which allows an addition of Nb lower than what is usually necessary to obtain properties of sufficient mechanical resistance from a niobium steel, titanium free. This minimal addition of Nb makes it possible to maintain good ductility properties. It also offers advantages economical considering the cost not negligible niobium.

    L'acier décrit ci-dessus est coulé en brames, qui sont réchauffées dans un four classique, par exemple un four à longerons mobiles ou un four poussant, pour qu'elles atteignent à coeur une température supérieure ou égale à 1000°C, ce qui suffit pour remettre en solution le niobium précipité.The steel described above is poured into slabs, which are reheated in a conventional oven, for example a traveling beam oven or a pushing oven, for that they reach a higher temperature at heart or equal to 1000 ° C, which is enough to restore solution of the precipitated niobium.

    On effectue alors un laminage à chaud sur un train de laminage classique, généralement en deux étapes:

    • un dégrossissage pour réaliser une ébauche de 35 mm ± 10 mm d'épaisseur, à une température moyenne de 1050°C, et
    • une finition pour réaliser une bande à chaud d'une épaisseur de 1 à 10 mm, en respectant une température minimale de laminage à chaud qui soit supérieure à la température de transformation de la phase γ à la phase α (Ar3).
    Hot rolling is then carried out on a conventional rolling train, generally in two stages:
    • roughing to make a blank 35 mm ± 10 mm thick, at an average temperature of 1050 ° C, and
    • a finish to produce a hot strip with a thickness of 1 to 10 mm, while respecting a minimum hot rolling temperature which is higher than the transformation temperature from the γ phase to the α phase (Ar 3 ).

    C'est entre 900°C et cette température de transformation que précipitent les nitrures de bore et les carbonitrures de niobium, avec par conséquent une fixation très précoce de l'azote.It is between 900 ° C and this temperature of transformation precipitated by boron nitrides and niobium carbonitrides, with consequently very early nitrogen fixation.

    La bande est alors refroidie de manière contrôlée et enfin bobinée à une température de l'ordre de 625°C ± 125°C.The strip is then cooled so controlled and finally wound at a temperature of around from 625 ° C ± 125 ° C.

    Après décapage en continu dans des lignes classiques (HC1 ou H2SO4), la bande est relaminée à froid, et ce avec un taux de réduction d'épaisseur compris entre 40 et 85 %.After continuous pickling in conventional lines (HC1 or H 2 SO 4 ), the strip is cold re-rolled, with a thickness reduction rate of between 40 and 85%.

    La bande laminée à froid est ensuite soumise à un recuit de recristallisation pour lui conférer les propriétés mécaniques nécessaires. Ce recuit peut s'effectuer sous forme d'un recuit statique, par exemple en bobine serrée ou expansée, à une température de l'ordre de 620-680°C, ou sous forme d'un recuit continu à une température de 680-850°C. 0e dernier recuit peut être combiné ou non avec un recouvrement éventuel par revêtement au trempé ou d'autres procédés.The cold rolled strip is then subjected to recrystallization annealing to give it the mechanical properties required. This annealing can take the form of static annealing, for example in a tight or expanded coil, at a temperature of around 620-680 ° C, or in the form of continuous annealing at a temperature of 680-850 ° C. Last annealing can be combined or not with a possible recovery by dip coating or other processes.

    Une dernière étape de laminage est encore effectuée, sous la forme d'un écrouissage final, afin de supprimer les phénomènes de "bandes de Lüders" et d'assurer une bonne rugosité de surface ainsi qu'une planéité du produit. A final rolling step is still performed, in the form of a final work hardening, in order to remove the phenomena of "Lüders bands" and ensure good surface roughness as well as flatness of the product.

    L'invention va à présent être expliquée de manière plus détaillée, à l'aide d'exemples donnés à titre non limitatif.The invention will now be explained in more detail, using examples given at non-limiting title.

    Exemple de comparaison 1Comparison example 1

    Acier à teneur en carbone extrêmement basse, sans niobium, mais avec addition de bore. Composition chimique (en 10-3 %). C Mn Si P S Al N2 B Nb 35 250 6 11 8 44 4,2 3,6 0 Bande laminée à chaud à une épaisseur de 3 mm. Température finale du laminage à chaud : 870°C Température de bobinage 620°C Décapage HCl Taux de réduction 66 % Bande laminée à froid à une épaisseur de 1 mm.
    Recuit de recristallisation en continu à 700°C pendant 40 sec. suivi d'une trempe à l'eau chaude à 50°C/sec. jusqu'à 400°C, application d'un vieillissement à 400°C pendant 120 sec. et refroidissement par tuyères jusqu'à une température de 120°C, décapage formique, rinçage, et séchage, puis application d'un taux d'écrouissage final de 0,8 %.    Extremely low carbon steel, without niobium, but with the addition of boron. Chemical composition (10 -3 %). VS Mn Yes P S Al N 2 B Nb 35 250 6 11 8 44 4.2 3.6 0 Hot rolled strip with a thickness of 3 mm. Final hot rolling temperature: 870 ° C Winding temperature 620 ° C HCl pickling Reduction rate 66% Cold rolled strip with a thickness of 1 mm.
    Continuous recrystallization annealing at 700 ° C for 40 sec. followed by quenching in hot water at 50 ° C / sec. up to 400 ° C, application of aging at 400 ° C for 120 sec. and cooling by nozzles to a temperature of 120 ° C., formic pickling, rinsing, and drying, then application of a final work hardening rate of 0.8%.

    Propriétés mécaniquesMechanical properties

    Limite d'élasticitéElasticity limit Rp 0,2 =Rp 0.2 = 235 MPa235 MPa Charge de ruptureBreaking load Rm =Rm = 340 Mpa340 Mpa Allongement à la ruptureElongation at break A% =A% = 38 %38% Coefficient d'écrouissageWork hardening coefficient n =n = 0,190/0,2000.190 / 0.200 Coefficient d'anisotropieAnisotropy coefficient r travers =r through = 1,351.35 Coefficient d'anisotropie planeCoefficient of plane anisotropy Δr =Δr = 0,3500.350 Coefficient d'anisotropie normaleCoefficient of normal anisotropy r moy.r avg. 1,11.1

    Exemple de comparaison 2Comparison example 2

    Même acier que celui utilisé dans l'exemple de comparaison 1.Same steel as that used in the example of comparison 1.

    On applique le même processus à la différence du recuit de recristallisation qui cette fois est statique à 640°C point froid (avec température maximale de 700°C) pendant 2 heures. Ensuite on achève le traitement de la manière décrite précédemment.We apply the same process to the difference recrystallization annealing which this time is static at 640 ° C cold point (with maximum temperature 700 ° C) for 2 hours. Then we finish the treatment as previously described.

    Propriétés mécaniquesMechanical properties

    Rp 0,2 =Rp 0.2 =
    175 MPa175 MPa
    Rm =Rm =
    310 Mpa310 MPa
    A% =A% =
    40 %40%
    n =n =
    0,2300.230
    r travers =r through =
    1,251.25
    Δr =Δr =
    0,0500.050
    r moy.r avg.
    1,011.01
    Exemple de comparaison 3Comparison example 3

    Acier au niobium à teneur en carbone extrêmement basse, sans bore. Composition chimique (en 10-3 %) C Mn Si P S Al N2 B Nb 50 350 8 12 6 40 6,0 0 50 Niobium steel with extremely low carbon content, without boron. Chemical composition (10 -3 %) VS Mn Yes P S Al N 2 B Nb 50 350 8 12 6 40 6.0 0 50

    La processus appliqué est le même que celui de l'exemple de comparaison 1, avec ces quelques différences: Température de bobinage : 600°C Taux de réduction : 50 % The process applied is the same as that of comparison example 1, with these few differences: Winding temperature: 600 ° C Reduction rate: 50%

    Recuit de recristallisation statique à 660°C point froid (avec température maximale de 680°C) pendant 2 heures, ou recuit continu à environ 790°C pendant 1 minute et vieillissement à 400°C pendant 180 secondes, puis application d'un taux d'écrouissaqe final de 1,4%.Static recrystallization annealing at 660 ° C cold spot (with a maximum temperature of 680 ° C) for 2 hours, or continuous annealing at around 790 ° C for 1 minute and aging at 400 ° C for 180 seconds, then application of a final hardening rate of 1.4%.

    Propriétés mécaniques (en long)Mechanical properties (in length)

    Rp 0,2 =Rp 0.2 =
    350 MPa350 MPa
    Rm =Rm =
    440 Mpa440 Mpa
    A% =A% =
    26 %26%
    n =n =
    0,1550.155
    r travers =r through =
    1,21.2
    r long =r long =
    0,7 0.7
    Δr =Δr =
    -0,250-0.250
    r moy.r avg.
    1,11.1
    Exemple 4Example 4

    Acier au niobium suivant l'invention, avec addition de bore. Composition chimique (en 10-3 %) C Mn Si P S Al N2 B Nb 55 300 7 14 3 50 5,6 4,5 7 Niobium steel according to the invention, with addition of boron. Chemical composition (10 -3 %) VS Mn Yes P S Al N 2 B Nb 55 300 7 14 3 50 5.6 4.5 7

    Le processus appliqué est le même que celui décrit dans l'exemple de comparaison 1, avec ces quelques différences : Température de bobinage : 500°C Taux de réduction : 80 % The process applied is the same as that described in comparison example 1, with these differences: Winding temperature: 500 ° C Reduction rate: 80%

    Recuit de recristallisation statique à 660°C point froid (avec une température maximale de 710°C) pendant 2 heures, puis application d'un taux d'écrouissage final de 1,5 %.Static recrystallization annealing at 660 ° C cold spot (with a maximum temperature of 710 ° C) for 2 hours, then application of a work hardening rate 1.5% final.

    Propriétés mécaniquesMechanical properties

    Rp 0,2 =Rp 0.2 =
    290 MPa290 MPa
    Rm =Rm =
    390 Mpa390 Mpa
    A% =A% =
    36,5 %36.5%
    n =n =
    0,1950.195
    r travers =r through =
    1,11.1
    Δr =Δr =
    -0,005-0.005
    r moy.r avg.
    1,01.0
    Exemple 5Example 5

    Acier au niobium suivant l'invention, avec addition de bore. Composition chimique (en 10-3 %) C Mn Si P S Al N2 B Nb 45 270 19 12 6 43 6,0 4,0 12 Niobium steel according to the invention, with addition of boron. Chemical composition (10 -3 %) VS Mn Yes P S Al N 2 B Nb 45 270 19 12 6 43 6.0 4.0 12

    Le processus appliqué est le même que celui décrit dans l'exemple de comparaison 1, avec ces quelques différences : Température finale du laminage à chaud : 875°C Température de bobinage : 640°C Taux de réduction : 55 % The process applied is the same as that described in comparison example 1, with these differences: Final hot rolling temperature: 875 ° C Winding temperature: 640 ° C Reduction rate: 55%

    Recuit continu de galvanisation à 850°C (température de pot de zinc : 480°C) avec vieillissement à 480°C, puis application d'un taux d'écrouissage final de 1,2 %.Continuous galvanizing annealing at 850 ° C (zinc pot temperature: 480 ° C) with aging at 480 ° C, then application of a work hardening rate 1.2% final.

    Propriétés mécaniquesMechanical properties

    Rp 0,2 =Rp 0.2 =
    300 MPa300 MPa
    Rm =Rm =
    400 Mpa400 Mpa
    A% =A% =
    33 %33%
    n =n =
    0,1750.175
    r travers =r through =
    1,11.1
    Δr =Δr =
    0,0050.005
    r moy.r avg.
    1,01.0
    Exemple de comparaison 6Comparison example 6

    Acier à teneur en carbone extrêmement basse, sans niobium, mais avec addition de zirconium. Composition chimique (en 10-3 %) C Mn Si P S Al N2 B Nb Zr 36 216 50 7 6 55 3,2 0 0 48 Extremely low carbon steel, without niobium, but with the addition of zirconium. Chemical composition (10 -3 %) VS Mn Yes P S Al N 2 B Nb Zr 36 216 50 7 6 55 3.2 0 0 48

    Le processus appliqué est le même que celui de l'exemple de comparaison 1, avec ces quelques différences : Température finale du laminage à chaud: 885°C. Température de bobinage : 650°C. Recuit de recristallisation statique (recuit base) à 610°C. Taux d'écrouissage final : 0,9 %. The process applied is the same as that of comparison example 1, with these few differences: Final hot rolling temperature: 885 ° C. Winding temperature: 650 ° C. Static recrystallization annealing (base annealing) at 610 ° C. Final work hardening rate: 0.9%.

    Propriétés mécaniquesMechanical properties

    Rp 0,2 =Rp 0.2 =
    224 MPa224 MPa
    Rm =Rm =
    351 Mpa351 Mpa
    A% =A% =
    37,6 %37.6%
    n =n =
    0,2060.206
    Δr =Δr =
    0,3080.308
    r moy.r avg.
    0,960.96
    Exemple 7Example 7

    Acier au niobium à teneur en carbone extrêmement basse, avec addition de zirconium. Composition chimique (en 10-3 %) C Mn Si P S Al N2 B Nb Zr 35 200 5 9 4 47 4,9 0 10 30 Niobium steel with extremely low carbon content, with the addition of zirconium. Chemical composition (10 -3 %) VS Mn Yes P S Al N 2 B Nb Zr 35 200 5 9 4 47 4.9 0 10 30

    Le processus appliqué est le même que celui de l'exemple de comparaison 1, avec ces quelques différences: Température de bobinage : 640°C. Taux de réduction : 58,3 %. Recuit de recristallisation statique (recuit base) à 700°C. Taux d'écrouissage final : 0,8 % The process applied is the same as that of comparison example 1, with these few differences: Winding temperature: 640 ° C. Reduction rate: 58.3%. Static recrystallization annealing (base annealing) at 700 ° C. Final work hardening rate: 0.8%

    Propriétés mécaniquesMechanical properties

    Rp 0,2 =Rp 0.2 =
    255 MPa255 MPa
    Rm =Rm =
    361 Mpa361 Mpa
    A% =A% =
    36,4 %36.4%
    n =n =
    0,1900.190
    Δr =Δr =
    0,0400.040
    r moy.r avg.
    1,011.01

    Ainsi qu'on peut le constater à partir de ces exemples, les aciers extra doux au bore ou au zirconium, sans niobium, s'ils sont bien ductiles, présentent des valeurs de résistance mécanique faibles à médiocres, relativement proches des valeurs minimales requises par les utilisateurs (RpO,2 supérieur ou égal à 220 MPa et Rm supérieur ou égal à 320 MPa).As can be seen from these examples, extra mild steels with boron or zirconium, without niobium, if they are well ductile, have low to poor mechanical strength values, relatively close to the minimum values required by users (R p O, 2 greater than or equal to 220 MPa and Rm greater than or equal to 320 MPa).

    L'acier extra doux au niobium, sans bore et sans zirconium, de l'exemple de comparaison 3 présente lui de bonnes valeurs de résistance mécanique, mais ses propriétés de ductilité sont parfaitement insatisfaisantes, alors qu'il est généralement demandé un allongement à la rupture supérieur ou égal à 32 % et un coefficient d'écrouissage supérieur ou égal à 0,170. Extra mild niobium steel, without boron and without zirconium, from comparison example 3 him good mechanical strength values but his ductility properties are perfectly unsatisfactory, while an extension is generally requested at break greater than or equal to 32% and a coefficient work hardening greater than or equal to 0.170.

    Les aciers au niobium suivant l'invention offrent à la fois des propriétés de résistance mécaniques largement supérieures aux limites inférieures usuelles et de bonnes propriétés de ductilité, en fournissant donc un compromis tout à fait favorable pour les traitements ultérieurs.Niobium steels according to the invention offer both mechanical resistance properties well above the lower limits usual and good ductility properties, in therefore providing an entirely favorable compromise for subsequent treatments.

    D'une manière particulièrement surprenante, les aciers au niobium suivant l'invention présentent, sur des bandes relaminées à froid et recuites, des propriétés mécaniques dans le plan de la bande qui sont sensiblement indépendantes de la direction par rapport au sens de laminage ainsi qu'une contraction rationelle en largeur sensiblement identique à une contraction rationelle en épaisseur. Ils réunissent donc toutes les conditions pour subir des traitements du type emboutissages difficiles et autres.In a particularly surprising way, the niobium steels according to the invention have, on cold-rolled and annealed strips, mechanical properties in the band plane which are significantly independent of management compared to in the sense of rolling as well as a rational contraction in width substantially identical to a contraction rational in thickness. They therefore bring together all conditions for undergoing stamping type treatments difficult and others.

    Claims (19)

    Acier au niobium, extra doux, calmé à l'aluminium et exempt de titane, pour produits plats laminés à froid et recuits, présentant une composition chimique en % en poids comprenant : au maximum 0,100 % de C, au maximum 1,000 % de Mn, au maximum 0,100 % de P, au maximum 0,020 % de S, au maximum 0,080 % de Al, au maximum 0,012 % de N, au maximum 0,500 % de Si,    le reste étant du fer et des impuretés residuelles,
       caractérisé en ce que cet acier contient une teneur en niobium stoechiométriquement inférieure à celle de l'azote et une teneur en bore ou en zirconium suffisante pour fixer l'azote non fixé par le niobium.    Niobium steel, extra mild, calmed with aluminum and free of titanium, for cold rolled and annealed flat products, with a chemical composition in% by weight comprising: maximum 0.100% of C, maximum 1,000% of Mn, maximum 0.100% of P, maximum 0.020% of S, maximum 0.080% Al, maximum 0.012% of N, maximum 0.500% of Si, the remainder being iron and residual impurities,
    characterized in that this steel contains a niobium content stoichiometrically lower than that of nitrogen and a boron or zirconium content sufficient to fix the nitrogen not fixed by the niobium.         Acier au niobium suivant la revendication 1, caractérisé en ce que la teneur en niobium est au maximum égale au quadruple de la teneur en N, de préférence au triple de celle-ci.Niobium steel according to claim 1, characterized in that the niobium content is at maximum equal to four times the N content, preferably three times that. Acier au niobium suivant l'une des revendications 1 et 2, caractérisé en ce qu'il contient une teneur en Nb inférieure à 0,040 % en poids, et de préférence comprise entre 0,005 et 0,030 % en poids.Niobium steel according to one of claims 1 and 2, characterized in that it contains a Nb content of less than 0.040% by weight, and preferably between 0.005 and 0.030% by weight. Acier au niobium suivant l'une quelconque des revendications 1 à 3, caractérisé en ce qu'il contient une teneur en bore comprise entre 0,0005 et 0,012 % en poids, de préférence entre 0,0015 et 0,012 % en poids.Niobium steel according to any one of claims 1 to 3, characterized in that it contains a boron content between 0.0005 and 0.012% by weight, preferably between 0.0015 and 0.012% in weight. Acier au niobium suivant l'une quelconque des revendications 1 à 3, caractérisé en ce qu'il contient une teneur en zirconium comprise entre 0,020 et 0,080 % en poids. Niobium steel according to any one of claims 1 to 3, characterized in that it contains a zirconium content between 0.020 and 0.080% by weight. Acier au niobium suivant l'une quelconque des revendications 1 à 5, caractérisé en ce qu'il contient une teneur en C égale ou supérieure à 0,010 % en poids.Niobium steel according to any one of claims 1 to 5, characterized in that it contains a C content of 0.010% or more in weight. Acier au niobium, suivant l'une quelconque des revendications 1 à 6, caractérisé en ce qu'il présente, sur des bandes relaminées à froid et recuites, une limite d'élasticité dont les valeurs minimales sont supérieures à 220 MPa et une charge de rupture dont les valeurs minimales sont supérieures à 320 MPa.Niobium steel, according to any one of claims 1 to 6, characterized in that it presents, on cold-rolled and annealed strips, a yield strength whose minimum values are greater than 220 MPa and a breaking load whose minimum values are greater than 320 MPa. Acier au niobium suivant la revendication 7, caractérisé en ce que la limite d'élasticité est supérieure à 250 MPa, de préférence supérieure à 280 MPa, et en ce que la charge de rupture est supérieure à 350 MPa, de préférence supérieure à 380 MPa.Niobium steel according to claim 7, characterized in that the elastic limit is greater than 250 MPa, preferably greater than 280 MPa, and in that the breaking load is greater than 350 MPa, preferably greater than 380 MPa. Acier au niobium, suivant l'une quelconque des revendications 1 à 8, caractérisé en ce qu'il présente, sur des bandes relaminées à froid et recuites, un allongement à la rupture supérieur ou égal à 32 % et un coefficient d'écrouissage supérieur ou égal à 0,17.Niobium steel, according to any one of claims 1 to 8, characterized in that it presents, on cold-rolled and annealed strips, an elongation at break greater than or equal to 32% and a work hardening coefficient greater than or equal to 0.17. Acier au niobium suivant l'une quelconque des revendications 1 à 9, caractérisé en ce qu'il présente, sur des bandes relaminées à froid et recuites, des propriétés mécaniques dans le plan de la bande qui sont quasi indépendantes de la direction par rapport au sens de laminage ainsi qu'une contraction rationelle en largeur quasi identique à une contraction rationelle en épaisseur.Niobium steel according to any one of claims 1 to 9, characterized in that it presents, on cold-rolled and annealed strips, mechanical properties in the band plane which are almost independent of management compared to direction of rolling as well as a rational contraction in width almost identical to a rational contraction in thickness. Acier au niobium suivant la revendication 10. caractérisé en ce qu'il présente un Δr situé entre -0,200 et +0,200, de préférence entre -0,100 et +0,100 et un r moyen situé entre 0,9 et 1,1.Niobium steel according to claim 10. characterized in that it has a Δr located between -0.200 and +0.200, preferably between -0.100 and +0.100 and an average r between 0.9 and 1.1. Procédé de fabrication de produits plats laminés à froid et recuits, à base d'un acier au niobium ayant une composition chimique suivant l'une quelconque des revendications 1 à 11, comprenant une coulée de cet acier en brames, un réchauffage des brames à une température supérieure ou égale à 1000°C, un laminage à chaud des brames pour former des bandes, avec une température finale de laminage supérieure à Ar3, un bobinage des bandes à une température de bobinage comprise entre 500 et 750°C, un laminage à froid des bandes avec un taux de réduction prédéterminé , un recuit de recristallisation, et un passage d'écrouissage final. Process for the production of annealed cold-rolled flat products based on a niobium steel having a chemical composition according to any one of Claims 1 to 11, comprising a casting of this steel in slabs, reheating the slabs to a temperature greater than or equal to 1000 ° C., hot rolling of the slabs to form strips, with a final rolling temperature higher than Ar 3 , winding the strips at a winding temperature between 500 and 750 ° C, cold rolling of the strips with a predetermined reduction rate, recrystallization annealing, and a passage of final hardening. Procédé de fabrication suivant la revendication 12, caractérisé en ce que le réchauffage des brames à lieu de préférence à une température de l'ordre de 1250°C.Manufacturing method according to claim 12, characterized in that the heating of the slabs preferably take place at a temperature of around at 1250 ° C. Procédé de fabrication suivant l'une des revendications 12 et 13, caractérisé en ce que la température finale de laminage à chaud est égale ou inférieure à 900°C.Manufacturing process according to one of claims 12 and 13, characterized in that the final hot rolling temperature is equal or less than 900 ° C. Procédé de fabrication suivant l'une des revendications 12 à 14, caractérisé en ce que le taux de réduction est de l'ordre de 40 à 85 %, de préférence de 55-80 %.Manufacturing process according to one of claims 12 to 14, characterized in that the rate of reduction is of the order of 40 to 85%, preferably of 55-80%. Procédé de fabrication suivant l'une des revendications 12 à 15, caractérisé en ce que le recuit de recristallisation est effectué sous la forme d'un recuit statique.Manufacturing process according to one of Claims 12 to 15, characterized in that the annealing recrystallization is carried out in the form of a static annealing. Procédé de fabrication suivant la revendication 16, caractérisé en ce que le recuit statique est effectué sur des bobines serrées ou expansées à une température de 620 à 680°C point froid. Manufacturing method according to claim 16, characterized in that the static annealing is performed on coils tight or expanded to a temperature from 620 to 680 ° C cold point. Procédé de fabrication suivant l'une des revendications 12 à 15, caractérisé en ce que le recuit de recristallisation est effectué sous la forme d'un recuit continu, avec ou sans revêtement.Manufacturing process according to one of Claims 12 to 15, characterized in that the annealing recrystallization is carried out in the form of a continuous annealing, with or without coating. Procédé de fabrication suivant la revendication 18, caractérisé en ce que le recuit de recristalisation continu est effectué à une température de 680 à 850°C.Manufacturing method according to claim 18, characterized in that the recrystallization annealing continuous is carried out at a temperature of 680 at 850 ° C.
    EP98200844A 1997-03-27 1998-03-18 Niobium containing steel and process for making flat products from this steel Revoked EP0870848B1 (en)

    Applications Claiming Priority (2)

    Application Number Priority Date Filing Date Title
    BE9700270A BE1011066A3 (en) 1997-03-27 1997-03-27 Niobium steel and method for manufacturing flat products from it.
    BE9700270 1997-03-27

    Publications (2)

    Publication Number Publication Date
    EP0870848A1 true EP0870848A1 (en) 1998-10-14
    EP0870848B1 EP0870848B1 (en) 2003-09-10

    Family

    ID=3890428

    Family Applications (1)

    Application Number Title Priority Date Filing Date
    EP98200844A Revoked EP0870848B1 (en) 1997-03-27 1998-03-18 Niobium containing steel and process for making flat products from this steel

    Country Status (7)

    Country Link
    EP (1) EP0870848B1 (en)
    AT (1) ATE249528T1 (en)
    BE (1) BE1011066A3 (en)
    DE (1) DE69817900T2 (en)
    DK (1) DK0870848T3 (en)
    ES (1) ES2207787T3 (en)
    PT (1) PT870848E (en)

    Cited By (4)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    WO2002059384A2 (en) * 2001-01-26 2002-08-01 Usinor High-strength isotropic steel, method for making steel plates and resulting plates
    FR2845694A1 (en) * 2002-10-14 2004-04-16 Usinor Fabrication of bake hardened steel strip for the production of automotive structural and appearance components, with or without anti-corrosion coatings
    US7365269B2 (en) 2002-10-09 2008-04-29 Prysmian Cavi E Sistemi Energia S.R.L. Method of screening the magnetic field generated by an electrical power transmission line and electrical power transmission line so screened
    RU2578280C2 (en) * 2011-09-06 2016-03-27 Арселормитталь Инвестигасьон И Дессарролло Сл Rolled steel which hardens through release of particles after hot forming and/or tempering in instrument, having very high strength and ductility, and method for production thereof

    Citations (10)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    JPS55122854A (en) * 1979-03-15 1980-09-20 Sumitomo Metal Ind Ltd Welded steel tube having superior butted portion toughness
    EP0101740A1 (en) * 1982-02-19 1984-03-07 Kawasaki Steel Corporation Process for manufacturing cold-rolled steel having excellent press moldability
    JPS59123721A (en) * 1982-12-29 1984-07-17 Kawasaki Steel Corp Production of cold rolled steel sheet having excellent processability
    JPS6160860A (en) * 1984-09-03 1986-03-28 Nippon Kokan Kk <Nkk> Zinc plated steel sheet for deep drawing, superior in plating adhesion and its manufacture
    JPS6164852A (en) * 1984-09-03 1986-04-03 Kawasaki Steel Corp Non-aging cold rolled steel sheet for press forming having extremely low anisotropy in plane
    WO1989007158A1 (en) * 1988-01-29 1989-08-10 Stahlwerke Peine-Salzgitter Ag Cold-rolled sheet or strip and process for manufacturing them
    EP0421087A2 (en) * 1989-08-09 1991-04-10 KABUSHIKI KAISHA KOBE SEIKO SHO also known as Kobe Steel Ltd. Method of manufacturing a steel sheet
    JPH04276026A (en) * 1991-02-28 1992-10-01 Nippon Steel Corp Manufacture of cold rolled steel sheet for deep drawing excellent in hardenability in coating baking and secondary workability
    EP0574814A2 (en) * 1992-06-08 1993-12-22 Kawasaki Steel Corporation High-strength cold-rolled steel sheet excelling in deep drawability and method of producing the same
    DE19547181C1 (en) * 1995-12-16 1996-10-10 Krupp Ag Hoesch Krupp Mfg. cold-rolled, high strength steel strip with good shapability

    Family Cites Families (2)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    US6126759A (en) * 1996-02-08 2000-10-03 Nkk Corporation Steel sheet for 2-piece battery can having excellent formability, anti secondary work embrittlement and corrosion resistance
    US5853903A (en) * 1996-05-07 1998-12-29 Nkk Corporation Steel sheet for excellent panel appearance and dent resistance after panel-forming

    Patent Citations (10)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    JPS55122854A (en) * 1979-03-15 1980-09-20 Sumitomo Metal Ind Ltd Welded steel tube having superior butted portion toughness
    EP0101740A1 (en) * 1982-02-19 1984-03-07 Kawasaki Steel Corporation Process for manufacturing cold-rolled steel having excellent press moldability
    JPS59123721A (en) * 1982-12-29 1984-07-17 Kawasaki Steel Corp Production of cold rolled steel sheet having excellent processability
    JPS6160860A (en) * 1984-09-03 1986-03-28 Nippon Kokan Kk <Nkk> Zinc plated steel sheet for deep drawing, superior in plating adhesion and its manufacture
    JPS6164852A (en) * 1984-09-03 1986-04-03 Kawasaki Steel Corp Non-aging cold rolled steel sheet for press forming having extremely low anisotropy in plane
    WO1989007158A1 (en) * 1988-01-29 1989-08-10 Stahlwerke Peine-Salzgitter Ag Cold-rolled sheet or strip and process for manufacturing them
    EP0421087A2 (en) * 1989-08-09 1991-04-10 KABUSHIKI KAISHA KOBE SEIKO SHO also known as Kobe Steel Ltd. Method of manufacturing a steel sheet
    JPH04276026A (en) * 1991-02-28 1992-10-01 Nippon Steel Corp Manufacture of cold rolled steel sheet for deep drawing excellent in hardenability in coating baking and secondary workability
    EP0574814A2 (en) * 1992-06-08 1993-12-22 Kawasaki Steel Corporation High-strength cold-rolled steel sheet excelling in deep drawability and method of producing the same
    DE19547181C1 (en) * 1995-12-16 1996-10-10 Krupp Ag Hoesch Krupp Mfg. cold-rolled, high strength steel strip with good shapability

    Non-Patent Citations (5)

    * Cited by examiner, † Cited by third party
    Title
    DATABASE WPI Section Ch Week 8045, Derwent World Patents Index; Class M23, AN 80-79688C, XP002046101 *
    DATABASE WPI Section Ch Week 8434, Derwent World Patents Index; Class M24, AN 84-211090, XP002046097 *
    DATABASE WPI Section Ch Week 8619, Derwent World Patents Index; Class M27, AN 86-121979, XP002046098 *
    DATABASE WPI Section Ch Week 8620, Derwent World Patents Index; Class M27, AN 86-127775, XP002046100 *
    DATABASE WPI Section Ch Week 9246, Derwent World Patents Index; Class M14, AN 92-376689, XP002046099 *

    Cited By (11)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    WO2002059384A2 (en) * 2001-01-26 2002-08-01 Usinor High-strength isotropic steel, method for making steel plates and resulting plates
    FR2820150A1 (en) * 2001-01-26 2002-08-02 Usinor HIGH-RESISTANCE ISOTROPIC STEEL, METHOD OF MANUFACTURING SHEETS AND SHEETS OBTAINED
    WO2002059384A3 (en) * 2001-01-26 2002-09-19 Usinor High-strength isotropic steel, method for making steel plates and resulting plates
    US7361237B2 (en) 2001-01-26 2008-04-22 Usinor High-strength isotropic steel, method for making steel plates and resulting plates
    KR100879084B1 (en) * 2001-01-26 2009-01-15 아르셀러미탈 프랑스 High-strength isotropic steel, method for making steel plates and resulting plates
    US7365269B2 (en) 2002-10-09 2008-04-29 Prysmian Cavi E Sistemi Energia S.R.L. Method of screening the magnetic field generated by an electrical power transmission line and electrical power transmission line so screened
    FR2845694A1 (en) * 2002-10-14 2004-04-16 Usinor Fabrication of bake hardened steel strip for the production of automotive structural and appearance components, with or without anti-corrosion coatings
    WO2004035838A1 (en) * 2002-10-14 2004-04-29 Usinor Method for making hardenable steel plates by firing, resulting steel plates
    CN100366760C (en) * 2002-10-14 2008-02-06 法国北方钢铁联合公司 Method for making hardenable steel plates by firing, resulting steel plates
    US7540928B2 (en) 2002-10-14 2009-06-02 Usinor Process for manufacturing bake hardening steel sheet, and steel sheet and parts thus obtained
    RU2578280C2 (en) * 2011-09-06 2016-03-27 Арселормитталь Инвестигасьон И Дессарролло Сл Rolled steel which hardens through release of particles after hot forming and/or tempering in instrument, having very high strength and ductility, and method for production thereof

    Also Published As

    Publication number Publication date
    DK0870848T3 (en) 2004-01-12
    DE69817900T2 (en) 2004-07-22
    EP0870848B1 (en) 2003-09-10
    BE1011066A3 (en) 1999-04-06
    PT870848E (en) 2004-01-30
    ES2207787T3 (en) 2004-06-01
    ATE249528T1 (en) 2003-09-15
    DE69817900D1 (en) 2003-10-16

    Similar Documents

    Publication Publication Date Title
    EP1195447B1 (en) Hot rolled steel plate, cold rolled steel plate and hot dip galvanized steel plate being excellent in strain aging hardening characteristics, and method for their production
    EP1592816A1 (en) Method of producing a cold-rolled band of dual-phase steel with a ferritic/martensitic structure and band thus obtained
    EP1427866B1 (en) Method for making rolled and welded tubes comprising a final drawing or hydroforming step and resulting rolled tube
    JP2003013177A (en) Hot-dip galvanized sheet steel with high ductility superior in press formability and strain aging hardening characteristics, and manufacturing method thereor
    JPH0349967B2 (en)
    FR2833617A1 (en) PROCESS FOR MANUFACTURING COLD ROLLED SHEATHES WITH HIGH RESISTANCE OF MICRO-ALLOY DUAL PHASE STEELS
    EP0870848B1 (en) Niobium containing steel and process for making flat products from this steel
    US6143100A (en) Bake-hardenable cold rolled steel sheet and method of producing same
    FR2761081A1 (en) PROCESS FOR MANUFACTURING AN ELECTRIC GRAIN-ORIENTED STEEL SHEET FOR THE MANUFACTURE OF IN PARTICULAR MAGNETIC CIRCUITS OF TRANSFORMERS
    EP0922777A1 (en) Flat product, such as sheet, made from ductile high-yield steel and process for manufacturing the same
    JP4670135B2 (en) Manufacturing method of hot-rolled steel sheet with excellent strain age hardening characteristics
    JP3925064B2 (en) Hot-dip galvanized steel sheet excellent in press formability and strain age hardening characteristics and method for producing the same
    JPH0144771B2 (en)
    JPH0559970B2 (en)
    EP0703298B1 (en) Method of manufacturing steels with good workability and shape stability
    US4159918A (en) Method of manufacturing a compound steel material of a high corrosion resistance
    JP3925063B2 (en) Cold-rolled steel sheet excellent in press formability and strain age hardening characteristics and method for producing the same
    JP3613139B2 (en) Method for producing hot-dip galvanized steel sheet
    EP1070148B1 (en) Method for making a hot-rolled steel strip for swaging
    BE1011557A4 (en) Steel with a high elasticity limit showing good ductility and a method of manufacturing this steel
    FR2753399A1 (en) HOT ROLLED STEEL PLATE FOR DEEP BINDING
    JP3111462B2 (en) Manufacturing method of high-strength bake hardenable steel sheet
    BE1002517A6 (en) Method for producing steel for embossing
    WO2012128272A1 (en) Method for winding hot-rolled maraging steel strip
    BE1002461A6 (en) Method for producing a steel strip with carbon through low temperaturerolling

    Legal Events

    Date Code Title Description
    PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

    Free format text: ORIGINAL CODE: 0009012

    AK Designated contracting states

    Kind code of ref document: A1

    Designated state(s): AT BE CH DE DK ES FI FR GB GR IE IT LI LU NL PT SE

    AX Request for extension of the european patent

    Free format text: AL;LT;LV;MK;RO;SI

    17P Request for examination filed

    Effective date: 19990113

    AKX Designation fees paid

    Free format text: AT BE CH DE DK ES FI FR GB GR IE IT LI LU NL PT SE

    17Q First examination report despatched

    Effective date: 20001018

    GRAH Despatch of communication of intention to grant a patent

    Free format text: ORIGINAL CODE: EPIDOS IGRA

    GRAH Despatch of communication of intention to grant a patent

    Free format text: ORIGINAL CODE: EPIDOS IGRA

    GRAA (expected) grant

    Free format text: ORIGINAL CODE: 0009210

    AK Designated contracting states

    Kind code of ref document: B1

    Designated state(s): AT BE CH DE DK ES FI FR GB GR IE IT LI LU NL PT SE

    RBV Designated contracting states (corrected)

    Designated state(s): AT BE CH DE DK ES FI FR GB GR IE IT LI LU NL PT SE

    REG Reference to a national code

    Ref country code: GB

    Ref legal event code: FG4D

    Free format text: NOT ENGLISH

    REG Reference to a national code

    Ref country code: CH

    Ref legal event code: EP

    REG Reference to a national code

    Ref country code: CH

    Ref legal event code: NV

    Representative=s name: DR. LUSUARDI AG

    REF Corresponds to:

    Ref document number: 69817900

    Country of ref document: DE

    Date of ref document: 20031016

    Kind code of ref document: P

    REG Reference to a national code

    Ref country code: IE

    Ref legal event code: FG4D

    Free format text: FRENCH

    GBT Gb: translation of ep patent filed (gb section 77(6)(a)/1977)

    Effective date: 20031212

    REG Reference to a national code

    Ref country code: SE

    Ref legal event code: TRGR

    REG Reference to a national code

    Ref country code: DK

    Ref legal event code: T3

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: FR

    Payment date: 20040122

    Year of fee payment: 7

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: NL

    Payment date: 20040127

    Year of fee payment: 7

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: LU

    Payment date: 20040130

    Year of fee payment: 7

    REG Reference to a national code

    Ref country code: GR

    Ref legal event code: EP

    Ref document number: 20030405023

    Country of ref document: GR

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: BE

    Payment date: 20040205

    Year of fee payment: 7

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: CH

    Payment date: 20040217

    Year of fee payment: 7

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: PT

    Payment date: 20040218

    Year of fee payment: 7

    Ref country code: IE

    Payment date: 20040218

    Year of fee payment: 7

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: GR

    Payment date: 20040224

    Year of fee payment: 7

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: SE

    Payment date: 20040302

    Year of fee payment: 7

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: AT

    Payment date: 20040303

    Year of fee payment: 7

    Ref country code: GB

    Payment date: 20040303

    Year of fee payment: 7

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: FI

    Payment date: 20040304

    Year of fee payment: 7

    Ref country code: DK

    Payment date: 20040304

    Year of fee payment: 7

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: DE

    Payment date: 20040305

    Year of fee payment: 7

    PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

    Ref country code: ES

    Payment date: 20040322

    Year of fee payment: 7

    REG Reference to a national code

    Ref country code: ES

    Ref legal event code: FG2A

    Ref document number: 2207787

    Country of ref document: ES

    Kind code of ref document: T3

    PLBQ Unpublished change to opponent data

    Free format text: ORIGINAL CODE: EPIDOS OPPO

    PLBI Opposition filed

    Free format text: ORIGINAL CODE: 0009260

    PLAX Notice of opposition and request to file observation + time limit sent

    Free format text: ORIGINAL CODE: EPIDOSNOBS2

    26 Opposition filed

    Opponent name: THYSSENKRUPP STAHL AG

    Effective date: 20040609

    NLR1 Nl: opposition has been filed with the epo

    Opponent name: THYSSENKRUPP STAHL AG

    PLAX Notice of opposition and request to file observation + time limit sent

    Free format text: ORIGINAL CODE: EPIDOSNOBS2

    RDAF Communication despatched that patent is revoked

    Free format text: ORIGINAL CODE: EPIDOSNREV1

    RDAG Patent revoked

    Free format text: ORIGINAL CODE: 0009271

    RDAE Information deleted related to despatch of communication that patent is revoked

    Free format text: ORIGINAL CODE: EPIDOSDREV1

    RDAF Communication despatched that patent is revoked

    Free format text: ORIGINAL CODE: EPIDOSNREV1

    RDAC Information related to revocation of patent modified

    Free format text: ORIGINAL CODE: 0009299REVO

    STAA Information on the status of an ep patent application or granted ep patent

    Free format text: STATUS: PATENT REVOKED

    REG Reference to a national code

    Ref country code: CH

    Ref legal event code: PL

    27W Patent revoked

    Effective date: 20050212

    GBPR Gb: patent revoked under art. 102 of the ep convention designating the uk as contracting state

    Free format text: 20050212

    R27W Patent revoked (corrected)

    Effective date: 20050212

    REG Reference to a national code

    Ref country code: PT

    Ref legal event code: MP4A

    Effective date: 20050629

    NLR2 Nl: decision of opposition

    Effective date: 20050212

    REG Reference to a national code

    Ref country code: SE

    Ref legal event code: ECNC

    PLAB Opposition data, opponent's data or that of the opponent's representative modified

    Free format text: ORIGINAL CODE: 0009299OPPO